1. Field of the Invention
The present invention relates to an apparatus for the formation and application of a sealing strip to seal the mouth of a filled sack, starting from a continuous strip of heat-sealable material.
2. Description of the Prior Art
At the present time, various systems exist for closing filled sacks made of heat-sealable material, in particular in sack filling machines.
Among these, the most simple and widely used involves heat sealing of the edges of the sack mouth, generally using a special device with heated bars, which seal the mouth of the sack together between them.
However, if the sack is filled with certain powdery or adhesive materials, the material with which the sack is filled is deposited on the inner surfaces of the sack itself, including the inner surfaces of the mouth, so that the above mentioned sealing operation becomes difficult or impossible.
In order to solve the problem mentioned above, a length of a strip of sheet material is used, generally the same material used to form the sack, and this strip is folded over and sealed to the opposite outer surfaces of the mouth of the sack, so as to seal it.
The systems for performing this operation are many, and include the manual application of the strip, or mechanical devices which fold the strip and assemble it on the mouth of the sack.
Obviously, manual application of this sealing strip is extremely uneconomical, as it involves a notable waste of manpower and time. On the other hand, the mechanical devices employed up to now have not shown themselves to be suitable for the job involved, so that application of the sealing strip is incorrect, resulting in faulty sealing of the mouth of the sack in question, and consequent leakage of the material contained therein when moved.